Field of the Disclosure
The present invention relates to organic light emitting diode (hereafter called as OLED) display devices, and more particularly, to device and method for controlling brightness of an OLED display device and sharing a computer system with a liquid crystal display device.
Discussion of the Related Art
The OLED display device is a self light emitting device which emits a light as an electron and a hole of an organic light emitting layer therein re-couples and is expected to be the next generation display device owing to high brightness, a low driving voltage and possibility of fabrication of an extra-thin device. Each of a plurality of pixels of the OLED display device is provided with an OLED pixel having an organic light emitting layer between an anode and a cathode, and a pixel circuit for driving the OLED pixel, independently. The pixel circuit is provided with a switching transistor, a capacitor, and a driving transistor, principally. The switching transistor charges a data signal to the capacitor in response to a scan pulse, and the driving transistor controls current intensity to be supplied to the OLED pixel according to a data voltage charged to the capacitor for controlling gray scale of the OLED pixel.
The OLED display device is provided with a data driver for sorting a plurality of reference gamma voltages supplied from an external gamma voltage generator into gamma voltages of different gray scales and converting a digital data into an analog data (a current or a voltage signal) by using the gamma voltages of different gray scales.
Opposite to this, the liquid crystal display device, which displays a picture by controlling a light transmissivity of liquid crystals on a light from a back light unit by varying an orientation of the liquid crystals according to the data signal, adjusts brightness of the back light unit according to a user's brightness adjusting signal.
Consequently, due to a difference of the brightness controlling systems of the OLED display device which is the self light emitting device and the liquid crystal display device which is a device that requires an additional light source, there has been difficulty in common use of the liquid crystal display device and the OLED display device in a computer system, such as a notebook computer.